1. Technical Field of the Invention
The present invention relates generally to medical devices for generating an angiogenic response in an interior wall of the heart using a percutaneous myocardial revascularization (PMR) procedure. More specifically, the present invention relates to an intravascular ultrasound PMR device having a needle for supplying the heart with an angiogenic material or contrasting agent.
2. Description of the Prior Art
There is a great deal of interest in improving the methods for treating cardiovascular disease. Traditionally, cardiovascular disease has been treated using procedures such as cardiovascular bypass surgery, coronary angioplasty, laser angioplasty and atherectomy. These techniques generally are aimed at bypassing or opening lesions in coronary vessels so as to restore and increase blood flow to the heart. In some patients, the number of lesions is so great, or the location so remote in the patient""s vasculature that restoring blood flow to the heart muscle is difficult. Therefore, it is often the case that cardiovascular disease requires alternative treatment such as percutaneous myocardial revascularization (PMR).
PMR was developed as a less invasive alternative to bypass surgery. PMR was inspired in part by observations that reptilian hearts are supplied primarily by blood perfusing directly from within heart chambers. In contrast, coronary vessels receiving blood from the aorta supply the human heart. PMR is performed by boring channels directly into the myocardium. This can be accomplished by a number of means including the insertion of a flexible catheter through the vasculature into the heart and boring holes into the myocardium. Positive results have been demonstrated in some human patients receiving these types of PMR treatments. These results are believed to be caused in part by increased blood flowing from within a heart chamber through channels formed by PMR to the myocardial tissue. Increased blood flow to the myocardium is also believed to be caused in part by the healing response to wound formation. Specifically, the formation of new blood vessels is believed to occur in response to the newly created wound.
Suitable PMR holes have been burned by laser, cut by mechanical means, removed by ultrasound devices, and burned by radio frequency current devices in a technique called radio frequency percutaneous myocardial revascularization (RF-PMR). In addition, catheter based needle injections of an angiogenic material directly into the myocardium has been developed in conjunction with RF-PMR. U.S. Pat. No. 6,063,082 to DeVore et al. entitled xe2x80x9cPercutaneous Myocardial Revascularization Basket Delivery System and Radiofrequency Therapeutic Devicexe2x80x9d discloses a method in which an angiogenic material can be delivered into a hole recently burned by RF current delivered through the needle. Unfortunately, in this method the angiogenic material may seep out of the hole created by the RF-PRM electrode, thus reducing the effectiveness of the angiogenic material.
U.S. Pat. No. 5,827,203 to Nita entitled xe2x80x9cUltrasound system and Method For Myocardial Revascularizationxe2x80x9d discloses a method that uses ultrasonic energy to accomplish PMR. Ultrasound PMR offers advantages over other PMR techniques in that the method is less invasive and that in some embodiments no tissue needs to be removed. The application of ultrasonic energy to an area of interest produces a thrombus required for angiogenesis without rupturing endocardial tissue. However, this method currently lacks the ability to deliver additional interventions, such as the delivery of angiogenic materials, to an area of interest. Thus, physicians are limited in their ability to use this method and are required to form channels in the heart wall if massaging an area of interest does not produce the desired effect. Further, if massaging an area of interest is insufficient to induce myocardial revascularization, the ultrasound device is used to bore channels. By including a means for delivering angiogenic materials, the need for using the ultrasound device to bore channels should be reduced.
New research conducted by the applicant suggests that the thrombus, caused by the application of ultrasonic energy, in and around the injury site contains the natural growth factors which cause the angiogenic response. Therefore, destruction of heart tissue, as with RF-PMR, may not be necessary to invoke an angiogenic response. Consequently, there is a need for a method of PMR that creates a natural angiogenic response without creating unnecessary injury to an area of interest. Additionally, it would be beneficial for this method to be able to deliver additional angiogenic material to an area of interest in order to minimize both the destruction of cardiac tissue and seepage.
A preferred embodiment of the present invention provides a minimally invasive device for the treatment of cardiovascular disease via ultrasound myocardial revascularization that additionally provides means for direct delivery of angiogenic materials. Combining ultrasound myocardial revascularization with an additional lumen for the delivery of angiogenic materials offers advantages over the prior art. Since it is believed that the thrombus contains the natural growth factors capable of facilitating an angiogenic response, this invention can accentuate the body""s own natural healing ability without destroying tissue. Further, since no myocardial tissue is destroyed, seepage of angiogenic materials is minimized. Finally, a contrasting agent can be delivered through the needle to enable the physician to image an area of interest.
In one embodiment of this invention, a needle is attached to the ultrasound PMR device adjacent to the catheter along the catheter""s longitudinal axis. Angiogenic materials or a contrasting agent can be delivered to an area of interest through the needle.
In another embodiment, the needle passes through the lumen of the ultrasound catheter. Angiogenic materials or a contrasting agent can be delivered to an area of interest through the needle.